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Computer programs that simulate the wave propagation phenomena involved in manifold tuning mechanisms are used extensively in the design and development of internal combustion engines. Most comprehensive engine simulation programs are based on the governing equations of one-dimensional gas flow as these provide a reasonable compromise between modelling accuracy and computational speed. The propagation of pressure waves through pipe junctions is, however, an intrinsically multi-dimensional phenomenon. The modelling of such junctions within a one-dimensional simulation represents a major challenge, since the geometry of the junction cannot be fully represented but can have a major influence on the flow. This paper introduces a new pressure-loss junction model which can mimic the directionality imposed by the angular relationship of the pipes forming a multi-pipe junction. A simple technique for estimating the pressure-loss data required by the model is also presented.

The volumetric efficiency of reciprocating internal combustion engines is a strong function of intake manifold configuration. A computationally efficient simulation technique is described which is based on the linearised one-dimensional conservation equations for distributed parameter systems and is amenable to the requirements of the designer in directly assessing the comparative merits of a large number of manifold configurations. Comparisons of measured and predicted volumetric efficiency curves are presented together with predicted results which illustrate the benefits to be obtained from variable geometry induction systems. The technique was found to be over 220 times faster than a comprehensive simulation program based on the method of characteristics.

The propagation of pressure waves through junctions in engine manifolds is an intrinsically multi-dimensional phenomenon. In the present work an inviscid two-dimensional model has been applied to the simulation of shock-wave propagation through 45° and 90° junctions: the results are compared with schlieren images and measured pressure-time histories. The HLLC integral state Riemann solver is used in a shock-capturing finite volume scheme, with second-order accuracy achieved via slope limiters. The model can successfully predict the evolution of the wave fronts through the junctions and the high frequency pressure oscillations induced by the transverse reflections. The calculation time is such as to make it feasible for inclusion, as a local multi-dimensional region, within a one-dimensional wave-action engine simulation.

Computer programs to simulate the gas dynamics of internal combustion engines are commonly used by manufacturers to aid optimization. These programs are typically one-dimensional and complex flow features are included as ‘special’ boundaries. One such boundary is the ‘pressure-loss’ junction model, which allows the inclusion of directionality effects brought about by the geometry of a manifold junction. The pressure-loss junction model requires empirical, steady-flow pressure-loss data, which is both time consuming and expensive to obtain, and also requires the junction to be manufactured before its performance can be established. This paper presents a technique for estimating the steady-flow data, thus obviating the need to perform these flow-tests.